Currently, what used the most often for petroleum exploration are the beam type pumping units, but this kind pumping machine has many disadvantages, such as low power transmission efficiency, low motor power utilization rate, and the stroke cannot be greatly improved.
The Chinese Patent No. 91228837.X publicized the linear pumping machine, which is composed of two special-shape chains, two rail sets (four rails), a commutator, an equalizer and a power system; the E-shape commutator and a middle beam are set up between the two rail sets and side beams are designed at both sides of the two rail sets; the rail sets are connected and fixed via connecting plates and designed with long circular grooves. Although this kind linear pumping unit has higher work efficiency and improved stroke, its structure is too complex, particularly, the four rails and the E-shape commutator are so complex that the required precision is hard to guarantee and manufacture and installation are difficult; moreover, as the rollers of the special-shape chains move in the long circular groove, the chains will get worn and lengthened and vibration or even damages will be caused to spare parts. Therefore, the linear pumping machine is difficult to maintain, not cost-efficient and has low reliability.